It is conventional in electrical control units to reduce electrical noise by providing on the printed circuit (PC) board noise suppression capacitors, in the form of Surface-Mounted Devices (SMD's) which are soldered to the associated printed conductor tracks on the board. The tracks which serve as the grounding terminal generally have soldered to them an S-shaped spring, a portion of which grips the edge of the PC board, and a free end of which rests under spring tension against a metal housing. This structure has the disadvantages that the springs, as mechanical elements, consume space and, as they age, degrade the spring contact to the metal housings, particularly if aluminum. They also present an excessively long path between noise suppression capacitor and grounding element and thus can radiate noise signals.
It is also known to design electrical control devices in which the PC board is glued onto a grounding plate or into a housing, e.g. of aluminum. The grounding plate and housing can additionally serve as cooling elements or heat sinks/radiators. In the case of PC boards of ceramic or glass, the adhesive must have a relatively large minimum thickness, due to the differing thermal coefficients of expansion of the ceramic or glass, on the one hand, and the aluminum housing, on the other hand, and further due to the need to compensate for manufacturing tolerances. The PC board is provided on its underside in the adhered region, with a relatively broad conductive track to which is connected, e.g. by through-plating, one side of the noise suppression capacitor mounted on the upper side of the PC board. Since the adhesive separates the aluminum element (grounding plate or housing) from the conductive track or patch, a capacitor is formed between the patch and the grounding plate or housing. However, in these prior art devices, the capacitance thus formed is very small, due to the relatively large distance between the two capacitor electrodes or plates (the patch an the grounding plate or housing), and resulting capacitance is too small to be operative for noise reduction certain frequency ranges, particularly the important FM frequency band.